The invention relates to a film scanner with an automatic focusing device in which the film images are shown line by line by means of an objective on at least one line sensor.
Manually focusing of film scanners inter alia has the drawback that the perception of the definition by human beings is irritated by the picture content. Furthermore, a relatively long dead time then exists, which leads to a transgression of the natural reaction and thus an “overwind” effect. This means that the user turns the adjusting knob, because the system cannot follow so fast and thus overshoots the goal to be attained. Especially with very brief scenes of, for example, 20s to 30s, as they often occur in commercials, it is thus hard to find the focal point.
It is true, various methods of automatic focusing are already known, for example, from EP 0 017 726 A1. However, they do not solve the problems discussed in the introductory paragraphs.